Process control systems are widely used in factories and/or plants in which products are manufactured or processes are controlled (e.g., chemical manufacturing, power plant control, etc.) Process control systems are also used in the harvesting of natural resources such as, for example, oil and gas drilling and handling processes, etc. Virtually any manufacturing process, resource harvesting process, etc. can be automated through the application of one or more process control systems.
The manner in which process control systems are implemented has evolved over the years. Older generations of process control systems were typically implemented using dedicated, centralized hardware. However, modern process control systems are typically implemented using a highly distributed network of workstations, intelligent controllers, smart field devices, and the like, some or all of which may perform a portion of an overall process control strategy or scheme. In particular, most modern process control systems include smart field devices and other process control components that are communicatively coupled to each other and/or to one or more controllers via one or more digital data busses. Of course, many of these modern process control systems may also include non-smart field devices such as, for example, 4-20 milliamp (mA) devices, 0-10 volts direct current (VDC) devices, etc., which are typically coupled directly to controllers as opposed to a shared digital data bus or the like.
In any event, field devices include, for example, input devices (e.g., devices such as sensors that provide status signals that are indicative of process control parameters such as, for example, temperature, pressure, flow rate, etc.), as well as control operators or actuators that perform actions in response to commands received from controllers and/or other field devices. For example, a controller may send signals to a valve to increase pressure or flow, to a heater or chiller to change a temperature, to a mixer to agitate ingredients in a process control system, etc.
One particularly important aspect of process control system design involves the manner in which field devices are communicatively coupled to each other, controllers and other systems or devices within a process control system. In general, the various communication channels, links and paths that enable the field devices to function within the process control system are commonly collectively referred to as an input/output (“I/O”) communication network.
Traditionally, many communication protocols and busses have been used to interface smart field devices to a controller or other control device. The control device (e.g., a controller) typically includes or is coupled to an I/O device having a communications protocol component, often termed the “master,” which activates and exchanges data with the smart field devices, often termed “slave” devices. In these known systems, the master must be configured to conform to the device specifications of the field devices (e.g., the particular communications protocol used by the field device). Consequently, there was a requirement for the user to always choose a particular protocol or set of devices supported by the manufacturer of the I/O device and/or to use different I/O devices or cards for each of the specific communication protocols needed to communicate with the various field devices used.